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Augmentation of Chains.


Flexible links are called tension elements; and fluid con-
nections, as between boiler and engine, or accumulator and
machine, are termed pressure elements, but the latter are always
connected to lower pairs. A pump is kinematically the same as a
ratchet, the valves being equivalent to pawls (see Fig. 450).

Augmentation of Chains is the multiplication of parts,
for convenience or the reduction of friction. Trains of gearing,
and anti-friction rollers (Fig. 451), are examples.

Summing up, mechanism may be divided into simple chains,
formed of rigid or flexible links, which are again united by higher
or lower pairs ; and all chains must be dosed, either by the chain
or by external force.*


Lower ( * Crank chains :

pairing, t 2, Screw chains :
High   [3- Pulley chains :


4.  Wheel chains:

5.  Cam chains:

1 Sliding and turning and   screw
J      pairs.

Tension and pressure elements.

Uniform motion.

Variable motion.

pairing. ^ 5. Ratchet chains:    Intermittent motion.

A driving and working end are recognised in each of thesey
corresponding to P and W respectively, and the

Velocity Ratio of P and W in Kinematic Chains
will now be investigated graphically. Considering the instan-

Friction closure is one form of force closure.